DESCRIPTION: (Applicant's abstract) This pilot project will develop transgenic techniques for ablating specific cells in the retina of the African Clawed Frog Xenopus laevis. The technology will be used for studying the role of photoreceptor interactions in the development, function and health of the retina. Specific Aims are to: 1. Develop strains of Xenopus with rodless retinas. 2. Place rod-specific ablation in Xenopus under the control of an inducible system. The strategy is to use existing cell-specific promoters and toxin genes to produce breeding lines of Xenopus in which specific photoreceptor populations, initially rods, can be eliminated in the embryo or the adult retina. Aim 1 will develop the molecular biological tools and then study the effects of rod death on the retina using light and electron microscopy. Aim 2 will place the toxin/promoter gene under the control of an inducible system permitting the timed ablation of specific retinal cells. Successful development of this technology should provide new methods for addressing such questions as: Why do dying rods kill cones in diseases such as retinitis pigmentosa and perhaps macular degeneration? How do retinal precursor cells interact to determine cell fate and differentiation? How is the neural circuitry of the retina established and maintained? It may provide new insights for developing potential therapies using gene delivery, growth factors and transplantation. It may also yield new methods for studying information processing and plasticity in the visual system. If successful, this project has high potential for opening new avenues of research on questions of retinal function in health and disease.